U.S. combat operations in Afghanistan are set to end after next year. So if the fighting stops, does the war on terror end? What does the end of the war mean for the detention center in Cuba and on drone strikes in Afghanistan?

STEVE INSKEEP, HOST:

Let's remember, American combat operations in Afghanistan are supposed to end after next year. So if they do, if the fighting stops in Afghanistan, at least for Americans, does that mean the war on terror is over?

The man who used to be the top lawyer at the Pentagon asked that question last year. He's Jeh Johnson and today, he's going to testify on Capitol Hill because he is President Obama's choice to lead the Department of Homeland Security. NPR's Carrie Johnson reports on what the end of the "forever war" might mean for Guantanamo and drone strikes.

CARRIE JOHNSON, BYLINE: Jeh Johnson says he vowed to serve his country after he saw the World Trade Center towers smoldering from his New York City office a dozen years ago. But in a speech last year at Oxford University, Johnson was the first government lawyer to raise this question:

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JEH JOHNSON: Now that efforts by the U.S. military against al-Qaida are in their 12th year, we must also ask ourselves: How will this conflict end?

CARRIE JOHNSON: Johnson predicted a tipping point, when so many al-Qaida leaders have been killed that the group won't be able to attack American soil. The U.S. drawdown in Afghanistan, scheduled for the end of 2014, represents a pivotal moment.

Steve Vladeck teaches law at American University in Washington.

STEVE VLADECK: The withdrawal of ground troops in Afghanistan is going to embolden arguments by detainees; that the entire justification for their initial capture and detention has, basically, fallen apart.

CARRIE JOHNSON: For years, the Obama administration has used a law Congress passed shortly after 9/11. It's known as the Authorization for Use of Military Force, or AUMF. And it's the basis for detaining people at Guantanamo prison, and at the Bagram Airbase in Afghanistan.

Jeh Johnson suggested that the end of that war authority could mean the end of the facility at Guantanamo.

JEH JOHNSON: We will also need to face the question of what to do with any members of al-Qaida who still remain in U.S. military detention.

CARRIE JOHNSON: A few months ago, President Obama called on Congress to limit or repeal the AUMF. Republican Sen. Lindsey Graham, of South Carolina, pushed the other way in an exchange with Michael Sheehan, an assistant secretary of defense.

SEN. LINDSEY GRAHAM: Do you agree with me, the war against radical Islam or terror will go on after the second term of President Obama?

MICHAEL SHEEHAN: Senator, in my judgment, this going to go on for quite a while and yes, beyond the second term of the president.

GRAHAM: And beyond this term of Congress?

SHEEHAN: Yes, sir. I think it's at least 10 to 20 years.

CARRIE JOHNSON: Others in the administration have been far more cautious about extending the war that far into the future. Still, national security experts - like Ben Wittes, of the Brookings Institution - say Guantanamo isn't likely to close anytime soon.

BEN WITTES: The end of the conflict, and the end of combat operations in Afghanistan, are not necessarily - legally speaking - the same thing.

CARRIE JOHNSON: Back in 1948, the Supreme Court ruled German enemy combatants from World War II could be held for years after the fighting ended. The Justice Department could use that precedent today. So that's the issue of what to do with detainees in places like Guantanamo.

Jeh Johnson's proposition that the war on terror has to end sometime, also applies to the use of drones. Again, American University's Steve Vladeck.

VLADECK: Part of this conversation is really not just about Afghanistan. It's about everywhere other than Afghanistan. And for the next 10 years where, exactly, is the U.S. government going to have the authority to use preemptive and potentially lethal military force?

CARRIE JOHNSON: Lethal military force including weaponized drones that have killed militants in Somalia, Yemen and Pakistan. Wittes, of the Brookings Institution, says the Obama administration has already taken steps to tighten its standards for targeted killing, to focus on the most senior operatives who pose the most serious threat. However it turns out, Wittes says, Johnson has raised some important questions.

WITTES: One of the ideas that lies behind war is that it's a temporary state of affairs, not a permanent state of affairs; and that the authorities that you exercise in war do not go on indefinitely and forever.

CARRIE JOHNSON: Building legal structures for this non-traditional conflict with al-Qaida, he says, could remain a substantial challenge well into the future.

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